Invasive evaluation of left ventricular diastolic performance.
Diastole can be divided into four phases: 1. isovolumic relaxation; 2. early filling; 3. diastasis; and 4. atrial systole. The amount of left ventricular (LV) filling that occurs during each of these phases depends on: 1. myocardial relaxation; 2. the passive characteristics of the LV; 3. the characteristics of the left atrium, pulmonary veins and mitral valve; and 4. the heart rate. When diastolic function is normal, the net effect of these factors results in LV filling sufficient to produce an adequate cardiac output, while mean pulmonary venous pressure is maintained below 12 mm Hg. Diastolic dysfunction is normally manifest as pulmonary congestion. In the absence of systolic dysfunction, abnormal diastolic performance is usually due to abnormal relaxation and/or changes in the passive LV characteristics, external compression or disease of the mitral valve and left atrium. Invasive studies can quantify the rate of myocardial relaxation from the time course of the fall of LV pressure during isovolumic relaxation and the passive LV properties from the LV diastolic pressure-volume relation. In addition, frame-by-frame analysis of contrast ventriculography and conductance determination of LV volume can quantify the pattern of LV diastolic filling. Normally, at rest, most LV filling occurs early in diastole. Conditions that produce diastolic dysfunction, such as LV hypertrophy and ischemia, are associated with reduced early diastolic filling and an augmented importance of atrial systole. It is important to recognize that such patterns can occur in patients without clinically apparent diastolic dysfunction and in normals if left atrial pressure is sufficiently elevated. Furthermore, a normal pattern can occur in patients with severe diastolic dysfunction. Reduced early diastolic filling in the absence of pulmonary congestion indicates the loss of diastolic reserve, since the left atrium is being used as a booster-pump. This pattern of diastolic filling in a patient with symptoms of pulmonary congestion suggests diastolic dysfunction, even if systolic LV performance is normal.
Little
W C
WC
Department of Medicine, Bowman Gray School of Medicine, Wake Forest University, Winston-Salem, North Carolina.
Downes
T R
TR
Applegate
R J
RJ
D016275:Atrial Function / Q000502:physiology; D002306:Cardiac Volume; D003971:Diastole / Q000502:physiology*; D006334:Heart Function Tests; D006339:Heart Rate; D006801:Humans; D008943:Mitral Valve / Q000502:physiology; D009126:Muscle Relaxation / Q000502:physiology; D009200:Myocardial Contraction / Q000502:physiology; D011312:Pressure; D011667:Pulmonary Veins / Q000502:physiology; D016277:Ventricular Function, Left / Q000502:physiology*